Mechanisms of North China Craton Destruction in the Southern Jilin Province in the Early to Middle Jurassic: Evidence From Adakite

ABSTRACT

The North China Craton (NCC) experienced significant destruction during the Mesozoic. However, considerable debate persists regarding the timing, mechanisms and deep dynamic processes of this craton destruction. This study investigates the petrogenesis, chronology, whole‐rock geochemistry, and Sr‐Nd‐Hf isotopic compositions of the Caoshan monzogranite and Diaoshuihu tonalite porphyry located in southern Jilin Province on the northeastern margin of the NCC. The investigation aims to elucidate the mechanisms of NCC destruction during the Early to Middle Jurassic, including lower crustal thickening, lithospheric thinning, and lower crustal delamination. The Caoshan monzogranite was emplaced in the late Early Jurassic (170.1 ± 2.3 Ma) and exhibits adakitic geochemical signatures, indicative of derivation from partial melting of thickened lower crust. The magma source comprised high‐pressure granulite facies rocks that underwent melting triggered by lithospheric thinning and heating from the asthenosphere. Melting produced an eclogite‐like residual assemblage, leading to a further density increase within the already thickened crust. The Diaoshuihu tonalite porphyry was emplaced during the late Middle Jurassic (168.6 ± 2.1 Ma). It exhibits adakitic geochemical characteristics indicative of an origin from the melting of delaminated lower crust. The magmatic source comprised high‐pressure granulite‐facies rocks of the thickened lower crust, which underwent partial melting upon being heated by the asthenospheric mantle subsequent to delamination. This melt also reacted with or was assimilated by mantle peridotite. Within the context of Paleo‐Pacific Plate subduction and compression during the Early to Middle Jurassic, the southern Jilin region experienced a dynamic sequence involving: thickening of the lower crust and lithospheric mantle; thermal‐mechanical/chemical erosion of the lithospheric mantle, transforming it into asthenospheric mantle and leading to progressive lithospheric thinning; concurrent delamination of the densified upper lithospheric mantle and the eclogitized lower crust.